1. Field of Invention
The present invention relates to a mask used for directly forming a thin layer pattern on the surface of a layer, a method of manufacturing such a mask, a method of manufacturing an organic electroluminescence (EL) device using such a mask, and an organic EL device manufactured using such a method.
2. Description of Related Art
In recent years, increasingly rapid advancements have been made in the art of an organic electroluminescence display device using organic electroluminescence elements (light emitting elements having a structure in which a luminescent layer formed of an organic material is disposed between an electrode and a cathode electrode) disposed for respective pixels. The organic electroluminescence display devices are expected to be used as emissive-type displays instead of the conventional liquid crystal display devices. Currently, known materials for forming a luminescent layer in an organic electroluminescence element can include an aluminum quinolino complex (Alq3) that is a low-molecular organic material and poly p-phenylenevinylene that is a macromolecular organic material.
A technique of forming a luminescent layer using a low-molecular organic material by vacuum evaporation is disclosed, for example, in Appl. Phys. Lett. 51(12), 21 September, 1987, p.913. A technique of forming a luminescent layer using a macromolecular organic material by a coating process is disclosed, for example, in Appl. Phys. Lett. 71(1), 7 July, 1997, p.34.
When forming a luminescent layer using a low-molecular organic material by vacuum evaporation, a metal mask (made of a metal such as stainless steel so as to have apertures corresponding to a thin-layer pattern to be formed) is conventionally used. In this technique, a thin-layer pattern corresponding to pixels can be directly formed on a substrate surface. In this technique, in contrast to a technique using a conjunction of a photolithographic process and an etching process in which a thin layer is first formed over the entire surface of a substrate and then the thin layer is patterned by photolithographic and etching processes, a thin layer having a desired pattern is directly formed using a metal mask.
However, the technique using a metal mask has the following problems. For example, if, in order to manufacture apertures so as to precisely correspond to a thin-layer pattern with a very small size, a metal mask having a small thickness is employed or if the distance between adjacent apertures is reduced, the mask can be bent or deformed during a process. In order to prevent the mask from being bent or deformed, it is often required that a tensile force be applied to the mask during the layer formation process. However, the tensile force can cause the apertures to be deformed. Thus, even if the metal mask is placed at a correct location, there is a possibility that the locations of the apertures deviate from the correct locations corresponding to the thin-layer pattern to be formed on a substrate.
A metal mask may be manufactured by forming apertures in a metal plate using a wet etching technique, a plating technique, a pressing technique, or a laser beam processing technique. However, in these conventional techniques, the size accuracy of apertures is limited to xc2x13 xcexcm, which is not sufficient to manufacture high-precision pixels.
In view of the above, it is an object of the present invention to provide a mask for use in directly producing a thin-film pattern on a substrate surface without having to perform a photolithographic process (that is, producing a thin film having a desired pattern on a substrate surface), having mask apertures formed with high enough accuracy (xc2x11 xcexcm, for example) to form high-precision pixels without causing the mask to be bent or deformed and without having to applying a tensile force to the mask during a thin-film formation process.
It is another object of the present invention to provide an organic electroluminescence display device having high-precision pixels manufactured by forming a thin-layer pattern serving as a layer (such as a luminescent layer) of the organic electroluminescence element using a mask according to the present invention.
According to an aspect of the present invention, there is provided a mask for use in manufacturing a thin-layer pattern serving as a layer of an organic electroluminescence element by means of vacuum evaporation. The mask can include an aperture corresponding to the thin-layer pattern and be formed of single crystal silicon and having a through-hole serving as the aperture formed by anisotropic wet etching using a crystal orientation dependence.
According to another aspect of the present invention, there is provided a mask for use in manufacturing a thin-layer pattern serving as a layer of an organic electroluminescence element by means of vacuum evaporation. The mask can include an aperture corresponding to the thin-layer pattern, and be formed of single crystal silicon so as to have a mask surface formed by a (100) surface of the single crystal silicon and have a through-hole with (111)-oriented walls serving as the aperture.
According to still another aspect of the present invention, there is provided a mask for use in manufacturing a thin layer having a predetermined pattern on a substrate surface. The mask can include an aperture corresponding to the pattern and be formed of single crystal silicon. The size of the aperture can change in a mask thickness direction such that the size has, at a boundary position, a minimum value corresponding to the size of the pattern and the size increasing toward both mask surfaces. Further, the distance from the boundary position to one mask surface and the distance from the boundary position to the opposite mask surface can be different from each other.
In this mask according to the present invention, preferably, the mask surface being formed by a (100)-surface of single crystal silicon, and the aperture including two wall portions that are tapered in opposite directions and that expand from the boundary position toward respective mask surfaces opposite to each other, and at least one wall portion being oriented in a (111)-direction.
In this mask according to the present invention, the mask can have a thin portion in which the aperture is formed and a thick portion in which no aperture is formed.
Preferably, the mask according to the present invention may be manufactured by a process having four features described below.
Firstly, a thin portion having a uniform thickness can be formed in a partial substrate area by etching a single crystal silicon substrate having a (100)-oriented crystal surface in a thickness direction of the single crystal silicon substrate. A first protective layer pattern having a through-hole corresponding to the aperture is formed on a first surface of the thin portion. A second protective layer pattern having a recessed portion can be formed at a location corresponding to the location of the aperture, on a second surface of the thin portion.
Secondly, after the above-described process, a through-hole can be formed in the thin portion at a location corresponding to the location of the aperture by anisotropic wet etching using the crystal orientation dependence such that the aperture size of the through-hole is greater at the first surface than at the boundary position and is smaller at the second surface than at the boundary position and than the size of the recessed portion.
Thirdly, the second protective layer pattern can be converted into a third protective layer pattern by performing wet etching such that the bottom of the recessed portion is perforated so that the recessed portion becomes a through-hole while maintaining the protective layer on the first surface.
Fourthly, the thin portion can be anisotropic wet-etched using the crystal orientation dependence such that a part of the thin portion exposed via the through-hole formed in the third protection layer pattern is etched until the aperture size at the boundary position becomes equal to a predetermined size.
According to still another aspect of the present invention, there is provided a method of manufacturing a mask for use in manufacturing a thin-layer pattern serving as a layer of an organic electroluminescence element by means of vacuum evaporation, the mask having an aperture corresponding to the thin-layer pattern. The method can include forming a through-hole as the aperture in which a single crystal silicon substrate having a (100)-oriented crystal surface by anisotropic wet etching using the crystal orientation dependence such that a through-hole having a (111)-oriented wall.
The method may preferably further include thinning the single crystal silicon substrate by etching in a thickness direction thereof such that a thin portion having a uniform thickness is formed in an partial area of the single crystal silicon substrate. After the step of thinning the single crystal silicon substrate, the through-hole can be formed in the thin portion by the anisotropic wet etching using the crystal orientation dependence.
According to another aspect of the present invention, there is provided a method of manufacturing a mask for use in manufacturing a thin layer having a predetermined pattern on a substrate surface, the mask having a aperture corresponding to the pattern. The method can include preparing a substrate including a base substrate, an insulating layer formed on one surface of the base substrate, and a single crystal silicon layer formed on the insulating layer. The method can further include removing the base substrate such that at least a partial area of the base substrate is removed over the entire thickness of the base substrate, and anisotropic etching the single crystal silicon layer remaining in the area from which the base substrate has been removed, so as to form a through-hole serving as the aperture in the single crystal silicon layer.
According to still another aspect of the present invention, there is provided a method of manufacturing an organic electroluminescence device. The method can include forming a thin layer pattern serving as a layer of the organic electroluminescence element by performing vacuum evaporation using a mask according to the present invention or a mask manufactured according to a mask production method according to the present invention.
According to still another aspect of the present invention, there is provided an organic electroluminescence device manufactured by an organic electroluminescence device production method according to the present invention.